Sketch (left) of the Milly dress that Michelle Obama wore in her National Portrait Gallery portrait (right).Michelle Smith; Portrait: Michelle LaVaughn Robinson Obama by Amy Sherald, oil on linen, 2018. National Portrait Gallery, Smithsonian Institution. The National Portrait Gallery is grateful to the following lead donors for their support of the Obama portraits: Kate Capshaw and Steven Spielberg; Judith Kern and Kent Whealy; Tommie L. Pegues and Donald A. Capoccia

When Michelle Smith designed a long, white halter dress with quilt-like abstract prints for her spring 2017 Milly collection, she had no idea it would become part of American history. But after Michelle Obama wore it for her official first lady portrait — painted by Amy Sherald and unveiled last month — she felt strongly that no one else should ever don it. Despite calls from desperate fashionistas begging for the dress, Smith is firm, telling Threads: “I’ve taken it out of the collection. It’s for Mrs. Obama only.”

Designer Michelle SmithDimitrios Kambouris/Getty Images

The designer, who showed her riotously colorful fall 2018 collection to great acclaim during NYFW, admits that she was initially shocked by the first lady’s pick.

“I was surprised and impressed that she chose a dress that was, perhaps, a little revealing for a first lady portrait,” Smith says. “I had imagined something more covered up. But I think that’s part of what’s so special about her beauty and elegance and relatability: That she’s sort of exposing herself, she’s being very real with us.”

Smith offered Obama several iterations of the gorgeous gown, but the first lady wanted to stick to the original runway version, with the exception of closing its open back. “I thought, after seeing the portrait, what a beautiful, perfect choice she made. I couldn’t imagine her in anything else.”